The present invention relates to a pressure control unit, in particular for pressure-fluid-actuatable dual-circuit brake systems for automotive vehicles.
Pressure control units of this type serve to reduce the braking pressure in the rear-axle brake circuit of a vehicle in relation to the pressure prevailing at the front-wheel brakes. To optimally adapt the brake behavior--under various load conditions of a vehicle and in consideration of the dynamic axle load distribution during the braking operation--to the brake behavior characterized by the ideal braking pressure characteristic curve, load-responsive pressure control units are provided. These control units are arranged so that there is variation of the change-over pressure on attainment of which pressure reduction commences.
A similar pressure control unit is known from the Brake Handbook Alfred Teves GmbH, 8th Edition 1984, Bartsch Publishing House, Ottobrunn, page 241 to 242. This load-responsive brake force regulator is provided with a locking device wherein a locking piston is arranged co-axially behind a regulating device, the locking piston will act directly on the regulating device on failure of a second brake circuit by moving into abutment with the regulating device and by keeping a control valve opened between the inlet and the outlet of the first brake circuit. This known construction necessitates a locking piston of complicated design and large overall length.